Amino Acids 14.5 – 14.8 By: Jean Turber, Kaitlin Clark & Kurstyn Pfleegor.
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Transcript of Amino Acids 14.5 – 14.8 By: Jean Turber, Kaitlin Clark & Kurstyn Pfleegor.
Amino Acids 14.5 – 14.8By: Jean Turber, Kaitlin Clark & Kurstyn Pfleegor
14.5 Uncommon Amino Acids Occur in some proteins, but not all. Derived from common amino acids. Produced in a process called post-translational
modification.‾ This is the process in which protein is
synthesized. Hydroxyproline & Hydroxylysine differ from their
parent amino acids ‾ Their found in connective tissue proteins
‾ collagen ‾ They have hydroxyl groups on their side chains.
14.5 Uncommon Amino Acids Continued Thyroxine differs from tyrosine.
‾ Has extra iodine-containing aromatic group on the side chain.
‾ Found only in the thyroid gland. ‾ Formed by post-translational modification
of tyrosine.‾ This process produces in the protein
thyroglobulin. ‾ Released as a hormone by proteolysis of
thyroglobulin.
14.5 Structures Proline Lysine Tyrosine
Thyroxine
14.6 How do Amino Acids Combine to Form Proteins? Amino Acid has a carboxyl group and an
amino group. The –COO group of one amino acid
molecule can combine with the –NH3 group of a second molecule.─ this reaction takes place in the cell.─ Produces an Amide.─ The two Amino Acids are joined together by an
peptide bond. (the linking of two amino acids) ─ Produces dipeptide.
14.6 Example Reaction Glycine + Alanine =
Glycyalanine
14.6 Continued Dipeptide
Two amino acids combined together. By adding more amino acids it will turn into a
tripeptide, tetrapeptide ect. Chain of hundreds or thousands of amino acids make up
protein that serve many functions in living organisms. The order of chain length goes by peptide (shortest),
polypeptide, proteins (longest). Polypeptides contain 30-50 amino acids
─ the amino acids in the chain are called residues One letter or three letter abbreviations are used to
represent proteins and peptides ( Ala, Gly, Lys)
14.6 Continued C-terminal amino acid is the residue
with the free –COO group. The amino acid at the end of a peptide
that has a free carboxyl group. N-terminal amino acid is the residue
with the free NH3 group. Has a free amino group.
Proteins are synthesized from N-terminal to C- terminal.
14.7 What are the Properties of Proteins?
The R group are called the side chains. The 6 atoms of the peptide backbone
lie on the same plane. 2 adjacent peptide bonds can rotate
relative to one another. The side chains determine the physical
and chemical properties of proteins.
14.7 Properties Proteins behave as zwitterions. Side chains of glutamic and aspartic acids provide
acidic groups. Lysine and Arginine provide basic groups. The isoelectric point of a protein occurs at the pH
equal number of positive and negative charges. Any pH above the isoelectric point the
molecules have a negative charge. Any pH below the isoelectric point the
molecules have a positive charge.
14.7 Properties Continued Hemoglobin has equal numbers of
acidic and basic groups. has a pH of 6.8
Serum albumin has more acidic groups than basic groups. pH of 4.9
Proteins act as buffers in the blood. Water solubility depends on repulsive
forces between like charges.
14.7 Properties Continued Protein molecules have a charge that causes them to
repel one another. When there are no repulsive forces protein molecules
clump together to form two or more molecules, reducing there solubility.
Primary structure describes the linear sequence of amino acids in the polypeptide chain.
Secondary structure refers to repeating patterns. Tertiary structure describes the overall conformation
of the polypeptide chain. Quarternary structure applies mainly to proteins
containing more than one poly peptide chain.
14.8 What is the Primary Structure of Proteins?
The primary structure consists of a sequence of amino acids in a chain
Decarboxylation Loss of CO2
Each protein has its own unique sequence of amino
Naming them starts at the N-terminal end The primary structure determines the
native secondary and tertiary structures
14.8 Protein Structures
14.8 Continued Particular sequences of amino acids
allow the whole chain to fold up or curl up
Different sequences may or may not affect the way it functions Cytochrome
In humans, chimpanzees, sheep, and other animals
Humans and chimpanzees have the same sequence
14.8 Continued People with diabetes use insulin from
cows, sheep, and hogs The difference in insulin is in the 8,9, and
10 positions of the A-chain and the C-terminal position of the B-chain Not as affective as human insulin
Human insulin is produced from bacteria Some people can be allergic to bovine
insulin
14.8 Hormones Two peptide hormones
Oxytocin Vasopressin
Identical structures Disulfide bonds
Difference in the amino acids in positions 2 & 7
Vasopressin increases the amount of water reabsorbed by the kidneys and raises blood pressure
14.8 Hormones Continued Oxytocin affects the contracts of the
uterus at child birth In the blood protein hemoglobin a
change in any one of the 146 amino acids is enough to cause sickle cell anemia
The sequence of an amino acids very important
Sequence of 10,000 protein and peptide molecules have been determined
14.8 Hormone Structures Oxytocin
Vasopressin